It's widely reported that Facebook is going to file for an IPO today, and likely that the offering will be in the $5 billion range. Time to start digging up your backyard bullion stash, right? Wrong. For the average guy the Facebook IPO is strictly Like, don't touch.

What's an IPO, Anyway?

IPO stands for Initial Public Offering which, in plain English, means a company putting itself on the stock market. Or, if you're in an antebellum mood, Facebook is announcing its debutante ball.

At its most fundamental level, an IPO is an opportunity for a company to raise lots and lots of money very quickly. In this case, Facebook will reportedly sell $5 billion worth of equity to outside investors, and will use that money to grow its business/buy yachts.

That $5 billion might sound like a lot, but it's actually about half of what had been rumored (before, uh, this newer rumor). And it is small, given that the total value of Facebook, public company, is expected to be a whopping $100 billion. If both of those numbers hold up, the lowball IPO is because Facebook doesn't want egg on its face; if you set the starting bid too high at a bachelor auction, no one gets a date.

So I Can Buy Facebook Shares Today?

Nope! Sorry. What's reportedly happening today (and almost certainly happening this week) is that Facebook is filing a propectus for its IPO with the Securities and Exchange Commission. The prospectus will be a fun read for the finance folk; it's an in-depth look at finances, projections, and how Facebook sees the competitive landscape.

It's also when Facebook finally says how much it thinks it's worth. Or rather, how much the investment bankers it hired (supposedly Morgan Stanley and a few others, in this case). And when I say "worth," I don't mean how much money it has in the bank or how much revenue it takes in. The gigantic number (that $100 billion) that you'll hear associated with Facebook today is a flimsy one, a guess. It's how much the company is expected to be worth as it continues to grow over time.

After the prospectus has been submitted, there's a "quiet period" while the SEC considers its validity. Bottom line: Assuming Facebook files all its papers today—and they're all in order—it's going to be a few months before Facebook shares are actually listed.

So I Can Buy Facebook Shares Then?

It's important to remember that lots and lots of shares of Facebook already exist. A year ago, a Goldman Sachs leak showed who owned how big a slice of the Facebook pie. This chart from Learnvest breaks it down nicely.

Two things from this: First, everyone on this chart is about to get very, very rich. The valuation at the time was $50 billion; today's could double that. They're the ones who are going to see a major payday; everyone else is going to be gambling that Facebook stock takes off like Google did back in 2004. Basically what I'm saying is nice work, Sean Parker!

Second is that even if you wanted to take make that gamble, there's a long, long line ahead of you. An IPO is not a democratic process. The banks who are helping Facebook decide how much it's worth, how many shares to offer, and at what price? They're not just in it for the (still very lucrative) commission. They also get first dibs in offering their big institutional clients—the Fidelities and Vanguards of the world—first dibs at shares in whatever the hot new offering is. And there hasn't been a hotter one than Facebook in years.

How bad is it? The AP points out that in a big IPO, institutional investors typically nab up to 90% of shares before Joe Investor can get involved. And chances are, there are plenty of Joe Investors with bigger wallets and better ins than you and I have. Shares will be available eventually, of course. Just as soon as the stock's risen enough that the big dogs feel comfortable cashing out.

So Why Does This Matter, Then?

In the short term, it doesn't. At least not financially, not to you. Not unless Facebook does something incredibly unorthodox to make more shares accessible to its 800 million users. That's not outside the realm of possibility; it's just a potential logistical nightmare. And when you're about to have a multi-billion dollar pay day, you want it to go as smoothly as possible.

But in the long term, Facebook being a public company has potentially huge repercussions. Private companies have the luxury of running themselves however they want. They can focus on long-term strategy instead of short-term gain. Public companies, though, have to march in front of their shareholders every three months and explain how and why they made—or lost—so much of other people's money.

That kind of pressure can make a company lose sight of what made it so successful in the first place. Facebook, in particular, will be immediately under fire for not doing more to monetize each individual user. Its earnings are dramatically below its projections; if it doesn't find a way to grow quickly, it'll have hell to pay. For a company that's already prone to overreaching, that anger could be the spark that lights a powder keg of privacy and Open Graph concerns.

For now though, don't sweat it. Let your banker friends swoon over Facebook's operating income and cash flow today. Raise a glass to Bono's huge payday in May. And get ready for Facebook's eventual assault on your wallet, a willing sacrifice to Mammon and Morgan Stanley.